Magnetic wheel numerical display device

ABSTRACT

A numerical display device having electrically energizable coil means mounted on a central winding form means for selectively providing a magnetic field selectively oriented in each of a plurality of discrete alignments in the region adjacent the coil means. A freely rotatable permanent magnet coupled with a symbol carrying means is positioned adjacent the coil means in said magnetic field for selectively assuming a corresponding plurality of discretely oriented alignments. A plurality of spaced symbols are positioned on an outer face of said symbol carrying means for selective positioning at a predetermined location in response to selected ones of said discrete alignments of said magnetic field.

i United States Patent [191 Kulka et al. 5] Oct. 16, 1973.

[54] ET WHEEL NU ER C L DI P 3,569,882 3/1971 McComb 340/378 MW DEVICE 1 Primary Examiner-Harold I. Pitts [76] n f zhfizg z z 2 Attorney-Blum, Moscovitz, Friedman & Kaplan a 9 Grace Rd., Lake Hiawatha, both of Ni [57] ABSTRACT [22] Filed, Nov 18 1970 v A numerical display device having electrically energiz- 7 i able coil means mounted on a central winding form [21] Appl. No.: 90,528 means for selectively providing a magnetic field selec- I tively oriented in each of a plurality of discrete align- [52] U S 340/378'R 340/378 MW ments in the region adjacent the coil means. A freely Hm 3/00 Gosh 5/00 rotatable permanent magnet coupled with a symbol [58] Fie'ld 34O/378 378 MW carrying means is positioned adjacent the coil means v in said magnetic field for selectively assuming a corret 56] References Cited sponding plurality of discretely oriented alignments. A plurality of spaced symbols are positioned on an outer UNITED STATES T v face of said symbol carrying means for selective-posi- 2,901,727 8/1959 Henn- Collins. 340/378- tioning at a predetermined location in response to segi pty-l; lected ones of said discrete alignments of said mageonc ic 3,478,288 ll/l9 69 Silverman.. 340/378 MW netlc field 3,478,349 11/ 1969 Buuck 340/378 MW 27 Claims, 21 Drawing Figures PATENTEDBBHS ms 3,766,549

SHEET 10F 8 INVENTORS ROBERT A. KULKA MICHAEL WIPLICH mvk' ATTORNE S PATENIEUEN 16 Ian 3, 766. 549

SHEET 2 BF 8 mom MICHAEL WlPLlCH ATTORNEYS PATENIEDHBI 15 I875 3. 766. 549

sum u 0F 8 ROBERT A. KULKA MICHAEL WIPLICH BY A TTORNEYS @ayM we MAGNETIC WHEEL NUMERICAL DISPLAY DEVICE BACKGROUND OF THE INVENTION This invention relates generally to numerical display devices of the type used to provide visual numerical outputs for devices producing binary coded output signals. For example, such devices may be'utilized as the output of a meter device in place of a dial or other means of indication. The known numerical display devices have proved expensive to operate and require substantial driving current. By providing a numerical display device of simple and compact construction, the advantages of the prior art arrangements have been overcome.

SUMMARY OF THE INVENTION Generally speaking, in accordance with the invention, a numerical display device is provided including central winding form means, electrically energizable coils means mounted on said central winding form means for selectively providing a magnetic field selectively oriented in each of a plurality of discrete alignments in the region adjacent said coil means, and permanent magnet means mounted for free rotation about an axis of rotation adjacent said coil means in said magnetic field for selectively assuming a corresponding plurality of discretely oriented alignments angularly spaced about the axis of rotation. A symbol carrying means is mounted for rotation with the permanent magnet means, said symbol carrying means being formed with an outer face having symbols spaced thereon for selective positioning at a predetermined location in response to selected ones of said discrete alignment of said magnetic field.

Said coil means may be adapted so that at least a portion of the magnetic field oriented in each of said plurality of discrete alignments extends at least in part through the region of and substantially normally to said axis of rotation. When so aligned, the coil means and permanent magnet means may be positioned in side-byside relation along the axis of rotation. The permanent magnet may include a bar magnet having north and south poles spaced substantially equal distances from the axis of rotation or a pair of permanent magnets mounted in spaced relation on a flux keeper means and having the north pole of one and the south pole of the other of said pair of permanent magnets facing said coil means.

The winding form means may be provided with a cylindrical well adapted to receive core means formed symmetrically relative to the axis of rotation, in which case the coil means would extend about the winding form means and core means. Said core means may be formed with a surface extending substantially normally to the axis of rotation, said surface having a plurality of projections extending radially therealong relative to the axis of rotation, at least one of said projections being in registration with and corresponding to each of said discrete alignments of said magnetic field, to define a locking means. In the alternative, said locking means may be formed of magnetic material having discrete portions thereof positioned at each of said plurality of discrete alignments of said magnetic field, as, for example, by a locking star member having the plurality of arm members extending in a radial direction from said axis of rotation. Such a locking star member would be aligned in side-by-side relation with said coil means and permanent magnets.

Said winding form means may be formed with an inner chamber for receiving said permanent magnet, said coil means being wound about said winding form. Such an embodiment would be provided with an annular flux keeper means positioned substantially concentrically with the axis of rotation and extending about said coil means.

In another embodiment, the winding form means may include a central support member having radially extending arms upon which are mounted bobbins, said coil means being wound on said bobbins. Said central support member may be formed of a magnetic material for serving as a core for said winding means and preferably is shaped as a cross.

The coil means may be adapted to produce a magnetic field at least portions of which, defining said plurality of discrete alignments, extends in a radial direction relative to the axis of rotation beyond the periphery of the coil means and winding form means. In such an embodiment, the permanent magnet means may include an annular permanent magnet having a pair of spaced distinct poles positioned concentric with the axis of rotation and having at least a portion thereof in the radially extending portions of said magnetic field. An annular flux keeper may be positioned outside of said annular permanent magnet.

'In still another embodiment of the arrangement according to the invention, said coil means may include printed circuit coil means mounted on said winding form means and aligned in side-by-side relation with said permanent magnet means along said axis of rotation. At least a portion of the winding form means would define a flux keeper means for providing a path for the flux produced by said printed circuit coil means. In this embodiment, said printed coil means may define a plurality of coils, each of said coils being defined by first and second printed circuit coil portions angularly spaced on said winding form means relative to the axis of rotation and connected in series for the production of a resultant magnetic field of selected angular alignment relative to the axis of rotation. Further, said winding form means may include at least a pair of winding form boards spaced along the axis of rotation with the permanent magnets therebetween, said printed circuit coil means being mounted on the facing surfaces of said pair of winding form boards.

The coil means may include first and second coil members positioned to produce respective magnetic fields substantially aligned along a first axis passing through said axis of rotation and third and fourth coil memberspositioned to produce magnetic fields aligned along a second axis passing through said axis of rotation and substantially normal to said first axis. A driving circuit means for providing energizing current to said coil means may be provided, said driving circuit means including switch means responsive to the presence of a 0 or 1 signal at each of four respective binary code positions. Circuit means may be provided for connecting the switch means and said coil members for the selective energization of said coil members by energizing currents of selected values whereby the magnetic field produced by said coils means at each of said discrete alignments corresponds to the sum of the magnetic fields produced by the energization of selected pairs of said coils by selected energizing currents in response to the state of said switch means. No two of said discrete alignments are spaced exactly 180 relative to the axis of rotation. Said circuit means may include resistive means for selectively controlling the value of the energizing current applied to each of the coil members at each state of the switch means. Resistive means connected in series with the four coil members may be provided for limiting the power dissipation in said coil members. The last-mentioned series connected resistor means may have non-linear resistive charcteristics, the resistance thereof increasing with increased current passing therethrough, for a proportionally increased reduction in power dissipation as the current passing through the coil member increases due to the selected states of said switch means. Further non-linear resistive means may be connected in series with at least one selected pair of said coil members for the selective angular positioning of certain of the discrete alignments of the coil means magnetic field.

In another embodiment, the coil means may include a first coil member positioned to produce a magnetic field substantially along a first axis passing through said axis of rotation and second, third and fourth coil members positioned to produce respective magnetic fields aligned substantially along a second axis passing through said axis of rotation and substantially normal to said first axis. A driving circuit means for such an embodiment would also include switch means responsive to the and l signals at each of at least four binary code positions, and have first circuit means for selectively connecting said first and second and said first or third coil members in series in response to the signal at the lowest of said binary code positions in response to the state of the switch means associated with said lowest binary code position, and second circuit means for selectively connecting the switch means associated with the balance of said decimal positions to said fourth coil member for the application of selected energizing currents to said fourth coil member in response to the state of said balance of said switch means.

In a further embodiment of the arrangement according to the invention, the coil means may include a first coil member adapted to produce a field aligned with said first axis passing through said axis of rotation and second and third coil members adapted to produce a magnetic field aligned with a second axis passing through said axis of rotation and skewed from said first axis. A driving circuit means for use in connection with such an embodiment would also include four switch means responsive to the 0 and 1 signal at each of four binary code positions respectively. Said driving circuit would include first circuit means for selectively applying an energizing current of a selected value to the series combination of said first and second coil members or to said first coil member, depending on the state of the switch means associated with the lowest of said binary code positions,and second circuit means for applying a selected energizing current of one ofa plurality of values to the third coil member in response to the state of the others of said switch means, said energizing current being selected so that no two of the discrete alignments of said winding means magnetic field are spaced exactly 180 apart relative to the axis of rotation. The latter result may be produced where said coil means magnetic field defines eleven substantially equal spaced discrete alignments.

Accordingly, it is an object of this invention to provide a numerical display device which is inexpensive to manufacture, compact of construction, and requires minimum driving currents.

Another object of the invention is to provide a numerical display device uniquely adapted to provide a decimal readout of a binary coded input signal.

A further object of the invention is to provide a numerical display device having locking means whereby the displayed number remains in position upon the withdrawal of the driving signal.

Still another object of the invention is to provide driving circuits for the numerical display device according to the invention for applying selected energizing currents to the coils of said numerical display device and, in some embodiments, particularly adapted to assist in the decoding from binary to decimal.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification and drawings.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of a group of numerical display devices according to the invention;

FIG. 2 is a sectional view taken along lines 2 2 of FIG. 1;

FIG. 3 is a sectional view taken along lines 3 3 of FIG. 2;

FIG. 4 is a prespective view ofa locking star member according to the invention;

FIG. 5 is a front elevational view of one embodiment of a winding form and core according to the invention;

FIG. 6 is a sectional view taken along lines 6 6 of FIG. 5;

FIG. 7 is a partial sectional view of an alternate embodiment of the permanent magnet means of the numerical display device according to the invention;

FIG. 8 is a sectioned front elevational view of a further embodiment of the numerical display device according to the invention;

FIG. 9 is a sectional view taken along lines 9 9 of FIG. 8;

FIG. 10 is a sectional side elevational view of still another embodiment of the numerical display device according to the invention;

FIG. 11 is a sectional view taken along lines 11- ll of FIG. 10;

FIG. 12 is a schematic and vector diagram of the coil structure of the embodiment of FIGS. 2 and 3;

FIG. 13 is a circuit diagram ofa driving circuit for use in conjunction with the coil structure of FIG. 12;

FIG. 14 is a fragmentary circuit diagram of an alternate embodiment of the driving circuit of FIG. 13;

FIG. 15 is a schematic and vector diagram of an alternate coil structure of the numerical display device according to the invention;

FIG. 16 is a circuit diagram of a driving circuit adapted for use in conjunction with the coil structure of FIG. 15;

FIG. 17 is a schematic and vector diagram of still another coil structure of the numerical display device according to the invention;

FIG. 18 is a driving circuit for use in conjunction with the coil structure of FIG. 17;

FIG. 19 is a front elevational view of a winding form and a core arrangement for use in conjunction with the winding structure of FIG. 18;

FIG. 20 is a sectioned side elevational view of still another embodiment of the numerical display device according to the invention; and

FIG. 21 is a front elevational view of a printed circuit board of the embodiment of FIG. 20.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a bank of three of a first embodiment of the numerical display device according to the invention is shown disposed in side by side relation with the viewing windows 12 thereof in substantial alignment. As more particularly shown in FIGS. 2 and 3, each display device includes a casing formed ofa low coercivity metal, such as aluminum, or a plastic material. The sides'of casing 14 are open, while the front face thereof is formed with a rectangular opening 16 adapted to receive said viewing window. For this purleaking into the adjacent display and affecting the operation thereof. On the other hand, such cover plates tend to shunt a portion of the operative magnetic field in said numerical display devices, thereby reducing the flux available for operating said display in the manner to be described below. A shielding end plate might be formed of silicon steel.

Mounted on end plate 22 is a printed circuit board 26 on which are deposited a plurality of conductor elements 28 defining the desired circuit connections to be more particularly described below. Said conductor elements terminate in a set of contact elements 30 which project beyond the rear face of case 14 to define a means for connecting driving circuitry to numerical display device 10. Also mounted on printed circuit board 26, by means of four standoff elements 32, is a winding form 34. Said winding form consists of a body portion 36 formed witha circular well 38 adapted to receive an annular magnetic core 40. Winding form 34 also includes four corner portions 42 adapted to project in a radial direction beyond the outer edges 44 of winding form body portion 36.

Said winding form corner portions serve to retain and position four orthagonally wound coils 48, 50, 52 and 54. The ends of said coils would be connected to conductor elements 28 for energization from the driving circuits. Both winding form 34 and standoff elements 32 are preferably formed of a plastic material. However, if desired, said standoff elements may be formed of a conducting material and may be utilized to couple selected ends of coils 48, 50, 52 and 54 to corresponding conductor elements 28 on printed circuit board 26. Symmetrical magnetic core 40 is preferably formed of a low retentivity magnetic material so as to have a minimum magnetic memory. For this purpose, a soft magnetic steel may be utilized.

Winding form body portion 36 is formed with a central aperture 56 therethrough in registration with a similar central aperture 58 extending through core 40. A bushing 60 is received within said aperture for mounting freely rotatable shaft 62. One end 64 of shaft 62 rests in a V-bearing 66. A second ring bearing 68 provides further support for shaft 62. A silicon fluid or grease 70 may be received within bushing 60 to aid in the damping of any possible oscillation of shaft 62. If desired, bearings 66 and 68 may be of the jewel type while bushing 60 may be brass. Both bushing 60 and shaft 62 are preferably formed of non-magnetic material to minimize drag on said shaft.

Mounted on the other end of shaft 62 is a cup shaped symbol bearing member 72 having a plurality of spaced symbols on outer face 74 of the annular portion thereof. Said spaced symbols are preferably numbers dimensioned to be visible through viewing window 12 when aligned therewith. For example, as shown in FIG. 1, the numeral 1 is shown visible through viewing window 12 of each of numerical display 10. Symbol bearing member 72 is preferably formed of a light weight material so as to have a minimum inertia. Foam plastic is particularly adapted for use in forming said symbol bearing member as it is both light weight and rigid, thereby providing a suitable surface for carrying the required symbols. Other materials which may be used for this purpose are thin aluminum and paper.

Also mounted on sahft 62 is a permanent bar magnet 75 having a north pole at end 76 and a south pole at end 77 thereof. Permanent magnet 75 is preferably symmetrical and balanced relative to shaft 62. The central portion thereof through which shaft 62 extends may be formed of magnetically soft steel, which is readily machinable. The remaining portion of said permanent magnet may be formed of bars of alnico or the like butting against said central portion to define said north and south poles. Coils 48, 50, 52 and 54 are selectively energizable for the selective production of a magnetic field in the region of permanent magnet 75 oriented in any of a plurality of discrete alignments. Permanent magnet 75 tends to align with said magnetic field for the positioning opposite viewing window 12 of the desired symbol carried on outer face 74 of symbol bearing member 72.

A numerical display device according to the invention is particularly adapted for the numbers of decimal numbers in response to binary coded acutating signals. In effect, the numerical display device according to the invention may serve as a decoder of said BCD signals as well as a numerical display arrangement. The operation of the embodiment of the arrangement according to the invention of FIGS. 2 and 3 may be more particularly understood in connection with the vector diagram shown in FIG. 12. In said vector diagram, coils 48 and 50 may be aligned along axis 76 to produce negative vector 78 and positive vector 80 respectively. Orthagonally wound relative to coils 48 and 50 are coils 52 and 54 which are aligned with axis 82. Coil 52 may selectively produce a magnetic field represented by vectors 84 and 86 while coil 54 may selectively produce a magnetic field represented by vectors 88 and 90. The

selective combination of two or more of the magnetic fields represented by vectors 78, 80, 84, 86, 88 and 90 will produce resultant magnetic fields aligned in at least 10 discrete alignments corresponding respectively to the 10 decimal digits through 9. The precise alignment of each of said discrete resultant magnetic fields will depend on the ampere-turns of the coils actuated to produce said field and, by the selective control of said ampere-turns, it is possible to define at least alignments spaced sufficiently to permit the provision of each of the 10 decimal digits in associated locations on outer face 74 of symbol bearing member 72. A driving circuit 92 for controlling the selective energization of coils 48, 50, 52 and 54 is shown in FIG. 13. In said circuit, an energization voltage is applied between positive terminal 94 and negative terminal 96. In the binary system, the decimal digits 0 through 9 are represented by four positions, each of which may be a l or a 0. Accordingly, the circuit 92 incorporates four switch means 98, 100, 102 and 104 responsive respectively to the signal on the l position, the 2 position, the 4 position and the 8" position of the binary input code. 1 position switch 98 is a two position switch. When armature 106 thereof engages fixed contact 108, the signal in the 1 position of the decimal code is 0, while when armature 106 engages fixed contact 110, the signal at said 1 position is a 1. The armatures of switch means 100, 102 and 104 close when the signal of their associated decimal position is a 1. Negative terminal 96 is connected by common line 112 to the armatures of each of switch means 98, 100, 102 and 104. Fixed terminal 108 of switch means 98 is connected by lines 114 and 115 to one end of coil 50. In like manner, fixed terminal 110 of said switch means is connected by lines 116 and 117 to one end of coil 48. Similarly, the fixed contact of switch means 100 is connected by lines 118 and 119 to one end of coil 54; the fixed terminal of switch means 102 is connected by lines 120 and 121 to one end of coil 52; and the fixed terminal of switch means 104 is connected by line 122, resistor 123, line 124 and line 121 to said end of coil 52. The other end of coils 48, 50, 52 and 54 are connected respectively through lines 125, 126, 127 and 128 to associated resistors 129, 130, 131 and 132. The latter resistors are all connected by common line 133 to resistor 134 which in turn is connected by line 135 to positive terminal 94. Fixed terminal 108 of switch means 98 is also connected by lines 114 and 136, resistor 137, line 138, diode 139 and lines 140, 141 and 119 to the end of coil 54, resistor 137 being connected through line 138 to the cathode of diode 139. Similarly, fixed terminal 110 is connected along lines 116 and 142, resistor 143, line 144, diode 145 and lines 141 and l 19 to said end of coil 54, resistor 143 being connected through line 144 to the cathode of diode 145.

Referring to FIGS. 12 and 13, circuit 92 operates as follows. When the binary coded number applied to circuit 92 is 0, switch means 100, 102 and 104 are open and armature 106 of switch means 98 engages fixed contact 108. In this position, current passes through coils 50 and 54. The magnetic field produced by coil 50, as represented by vector 80, depends on the number of turns of said coil and the value of resistor 130 while the magnetic field produced by coil 54 depends on the number of turns thereof, and the value of resistors 132 and 137. The resultant magnetic field is aligned along dashed line 146 of FIG. 12. When the binary coded number is 1 armature 106 engages fixed contact 110 of switch means 98 to apply ,current to coils 48 and 54, thereby producing magnetic fields represented by vectors 78 and 88 respectively. The magnitude of the magnetic field represented by vector 78 is determined by the number of turns of coil 48 and the value of resistor 129 while the value of the magnetic field represented by vector 88 is determined by the number of turns of coil 54 and the value of resistors 132 and 143. The resultant magnetic field is positioned along dashed line 148 of FIG. 12. The relatively small vector generated by coil 54 in each of the two circumstances described above is utilized to offset the alignment of the O and 1 positions from the 180 relation between vectors 78 and 80. In the absence of such an offset, the numerical display device according to the invention might not respond to a change of input signal from 0 to l and vice versa due to the lack of rotative force on permanent magnet produced by a 180 change in vector direction.

The presence of a 1 signal at the 2 position of the input binary signal would close switch means 100 to provide a current through coil 54 for the production of a magnetic field represented by vector 90. The closing of switch means 100 also deactivates the abovedescribed bypass by applying the same voltage on both sides of diodes 139 and 145. The magnitude of the magnetic field represented by vector 90 is determined by the number of turns in coil 54 and the value of resistor 132. The presence of a 1 signal in the 4 position closes switch means 102, the resultant current through coil 52 producing vector 84, the magnitude of which is governed by the number of turns in coil 52 and the magnitude of resistor 131. Should a I signal appear at position 8 of the binary signal, coil 52 would again be energized to produce a magnetic field represented by vector 86, the magnitude of which is governed by the number of turns of coil 52 and the value of resistors 131 and 123.

From the foregoing, the application of a binary 2 to circuit 92 would produce a resultant magnetic field represented by dashed line 150, representing the sum of vectors and 90. In like manner, a binary 3 would produce a magnetic field aligned along dashed line 152 representing the sum of vectors 78 and a binary 4 would produce a magnetic field aligned along dashed line 154 representing the sum of vectors 80, 12. and 88; a binary 5 would produce a magnetic dashed along dahsed line 156 representing the sum of vectors 78, 84 and 86; a binary 6 would produce a magnetic field along dashed line 158 representing the sum of vectors 80, 84 and 90; a binary 7 signal would produce a magnetic field aligned along dashed line 160 representing the sum of vectors 78, 84 and 90; a binary 8 would produce a magnetic field aligned along dashed line 162 representing the sum of vectors 80, 86 and 88; and a binary 9 would produce a magnetic field aligned along line 164 representing the sum of vectors 78, 84 and 88.

In the foregoing embodiment, the 10 discrete alignments of the magnetic field produced within numerical display device 10 are not uniformly angularly spaced. Further, nor would the numbers 0 through 9 appearing on the outer face 74 of symbol bearing member 72 be in numerical sequence. Rather, the numbers would be positioned along said annular face to correspond with the relative positions of the resultant magnetic fields shown in FIG. in FIG. By adjusting the magnetic field produced by each of coils 48, 50, 52 and 54, the relative positioning of the respective resultant magnetic fields may be selectively adjusted. While separate resistors 129, 130, 131 and 132 are shown in the embodiment of FIG. 13, these resistors could be dispensed with if each of the corresponding windings had the required proportional number of turns. However, as a practical matter, the manufacture of the numerical display device according to the invention would be simplified by winding said coils uniformly and selectively adjusting the ampere turns by the selection of resistors 129, 130, 131 and 132. Diodes 139 and 145 may be dispensed with if desired.

Resistor 134 is provided in series with the power supply to limit the current, and therefore the power dissipation in the numerical display device according to the invention. An examination of the vector diagram of FIG. 12 reveals that coils 52 and 54 draw a substantially greater amount of current than coils 48 and 50. Resistor 34 does not affect the ampere-turns ratio between the various vectors, and accordingly, the alignment of the resultant magnetic fields. Only the magnitudes of the resultant magnetic fields are affected. By selection of resistor 134, the magnitude of said resultant magnetic fields are selected to exceed the value necessary to displace shaft 62, and permanent magnet 75 and symbol bearing member 72 mounted thereon,- while minimizing the power dissipated in the coils, thereby permitting the operation of the device at lower currents than would otherwise be possible. In an alternate embodiment of the circuit 92, resistor 134 may be of the non-linear type having a value which increases with increasing current. Such a non-linear resistor might be a tungsten filament light bulb. Such tungsten filament light bulbs have a ratio of about 4 to 1 between hot and cold resistances. By using such a non-linear resistor, the effect of the resistor in the circuit is minimized in the presence of low currents, thereby avoiding the changing of the vector magnitudes produced by the relatively low-current coils. As applied to this alternate embodiment, a tungsten light bulb could be operated below its nominal current, thereby increasing the life thereof. As such values, the operating ratio between hot and cold resistances would be on the order of 2 to l or 3 to 2.

Still a further embodiment of circuit 92 is shown in FIG. 14, wherein resistors 131 and 132, connected respectively to coils 52 and 54 are connected to a common line 166, which in turn is connected to a nonlinear resistor 168, of the type described above, said non-linear resistor being connected to common line 133. Non-linear resistor 168 would serve to adjust the angular position of the resultant magnetic field representative of binary numbers 4 and 5 into positions such that the possible resultant fields are aligned in eleven substantially uniformly spaced positions. Such uniform spacing would provide an eleventh position which could be used for an additional symbol such as a decimal point or a plus or minus sign. By providing resistor 168 as a non-linear resistor, the magnitude of vectors 84 and 90 produced by coils 52 and 54 respectively would be affected only when both of said coils are energized. Resistor 168 would be selected to have a minimum effect at the relatively low current present when only one of said coils are energized.

A second embodiment of the coil structure of the numerical display device according to the invention is shown schematically in FIG. 15, a driving circuit for driving the coil structure of FIG. 15 being shown in FIG. 16. The coil structure of FIG. 15 consists of a coil 172 aligned along axis 174 and adapted to produce a positive magnetic field represented by vector 176 when a positive voltage is applied to terminal 178 thereof. Coil 172 is adapted to produce a magnetic field represented by negative vector 180 when a negative voltage is applied to terminal 178. Coils 182, 184 and 186 are wound orthagonally to coil 172 along axis 188. Coil 182 is adapted to produce a magnetic field represented by any one of negative vectors 190 and 192 and positive vectors 194 and 196, depending on the ampereturns present in said coil. Coils 184 and 186 are each adapted to produce a magnetic field represented by negative vector 198. The O alignment is produced by the sum of vectors 176 and 198 and is represented by dashed line 200. Similarly, the 1 alignment is represented by the sum of vectors 180 and 198 and is represented by dashed line 202. Referring to FIG. 16, these resultant magnetic fields are produced by coils 172, 184, and 186. Specifically, a power supply is applied between positive terminal 204 and negative terminal 206 of circuit 170. A two position binary 1 position switching means 208 is provided having an armature 209 adapted to engage fixed terminal 210 when a 0 signal is received in the 1 position of the binary code. Armature 209 is adapted to engage fixed terminal 211 when a l-signal is received on said 1 position of said binary code. Fixed terminal 210 is connected through line 211, coil 184, line 212, resistor 213 and lines 214 and 215 to positive terminal 204. Similarly, fixed terminal 211 is connected by line 216, coil 186, line 217, resistor 218 and lines 219 and 220 to negative terminal 206. Armature 209 of switch means 208 is connected along line 221, resistor 222, and line 223 to terminal 178 of coil 172, said coil being in turn connected along line 224 to ground. By the foregoing circuitry, coil 172 and coil 184 are connected in series with positive terminal 204 of the power source when a 0 signal is present at the 1 position of the binary code while,coil 172 is connected in series with coil 186 and the negative terminal 206 of said power source when a 1 signal is present at said 1 binary code position.

Switch means 225, 226 and 227 are provided for actuation in response to the signal at the 2, 4, and 8 positions respectively of the binary code. Switch means 225 includes a pair of ganged armatures 228 and 229 adapted to engage fixed contacts 230 and 231 respectively when a 1 signal is detected at the 2 position of the binary code. Armature 229 is also adapted to engage fixed contact 232 when a 0 signal is detected at said 2 position. Similarly, switch means 226 is provided with a pair of ganged armatures 233 and 234 adapted to engage fixed terminals 235 and 236 respectively when a 1 signal is present at the 4 position of said binary code. Armature 233 of switch means 226 is also adapted to engage fixed terminal 237 when a 0 signal is present at said 4 position. Positive terminal 204 of said power source is connected along lines 215, 238 and 239, resistor 240 and line 241 to fixed terminal 230 of switch means 225. The armature 228 of said switch means is connected to fixed terminal 235 by line 242 while armature 233 of switch means 226 is connected by lines243 and 244 to coil 182. Negative terminal 206 of said power source is connected along line 220 and 245 to armature 229 of switch means 225. Fixed terminal 231 of said switch means is connected along line 246, resistor 247 and line 248 to fixed terminal 237 of switch means 226. Fixed terminal 232 is connected along line 249 to fixed terminal 236 of switch means 226, while armature 234 of switch means 226 is connected along line 250, resistor 251, and line 252 and 244 to coil 182. Coil 182 is connected by line 253 to ground.

Resistor 247 is selected so that the magnetic field in coil 182 is as represented by vector 192 for the production of resultant magnetic fields representative of the decimal 2 and 3 positions as represented by dashed lines and 254 and 256 respectively. The resultant magnetic field represented by dashed line 254 represents the sum of vectors 176, 192 and 198 while the resultant magnetic field represented by dashed line 256 represents the sum of the magnetic fields represented by vectors 180, 192 and 198. Resistor 251 is selected to produce a magnetic field in coil 182 representative of vector 190 to produce the resultant magnetic field aligned in decimal position 4 and 5 as represented by dashed lines 258 and 260 respectively. The resultant field for decimal position 4 is produced by the sum of the magnetic fields represented by vectors 176, 190 and 198 while the resultant magnetic field of position 5 is produced by the sum of the magnetic fields represented by vectors 180, 190 and 198.

Resistor 240 produces the magnetic field in coil 182 represented by vector 196 for the production of the resultant magnetic field representative of decimal positions 6 and 7, which are represented by dashed lines 262 and 264 respectively. Decimal position 6 is produced by the sum of the magnetic field represented by vectors 176, 196 and 198 while decimal position 7 is produced by the sum of the magnetic fields represented by vectors 180, 196 and 198.

Switch means 227 is associated with the 8 binary code position and is connected by lines 265, 238 and 215 to positive terminal 204 of the power source, and by line 266, resistor 267, and lines 268 and 244 to coil 182. Said switch means closes upon the presence of a 1 signal at said 8 position for the production of a magnetic field represented by vector 194 in coil 182, the magnitude of said vector being governed by the magnitude of resistor 267. The latter circuitry produces decimal positions 8 and 9 as represented by dashed lines 270 and 272 respectively. The resultant magnetic field of decimal position 8 is produced by the sum of the magnetic field represented by vectors 176, 194 and 198, while the resultant magnetic field represented by decimal position 9 is produced by the magnetic field represented by the sum of vectors 180, 194 and 198.

The embodiment of FIGS. 15 and 16 produces eleven substantially equally spaced positions, 10 of which are occupied by decimal digits 0 through 9, the eleventh being either unused or used for other symbols such as signs or decimal points. The eleven position embodiment insures that no two positions are spaced 180. The embodiment of FIGS. and 16 differs from the embodiment of FIGS. 12, 13 and 14 in that the circuitry of circuit 170 performs part of the decoding function. This embodiment permits greater flexibility in dictating the order of the numerals as positioned on outer face 74 of symbol bearing member 72. However, as in the case of the first embodiment, the embodiment of FIGS. 15 and 16 does not provide the numerals in numerical order.

Still a further embodiment of the coil structure and driving circuit according to the invention is shown in FIGS. 17, 18 and 19. The structure of this third embodiment is similar in operation to the embodiment of FIGS. 15 and 16 except that only three coils are utilized, the effect of the fourth coil being produced by the use of a skewed core. Specifically, coil 274 is provided in alignment with axis 276 for the production of a magnetic field represented by vector 278 when a positive voltage is applied to terminal 280 thereof. Coil 274 is also adapted to produce a magnetic field represented by negative vector 282 when a negative voltage is applied to terminal 280 thereof. Both positive vector 278 and negative vector 282 are aligned with axis 276. Coils 284 and 286 are also wound on the same core. However, they are not wound on orthagonal axis 288, but rather, are wound along an axis 290 skewed from axis 288 by a selected angle. FIG. 18 shows a core adapted for producing this result. Said core consists of a winding form 292 adapted for substitution for winding form 34 of the embodiment of FIGS. 2 and 3. Winding form 292 includes a circular central well 294 for receiving a symmetrical magnetic core 296 similar in structure and function to magnetic core 40 of the embodiment of FIGS. 2 and 3. Winding form 292 is provided with a pair of spaced parallel notches 298 and 300 for receiving coil 274. A second pair of spaced notches 302 and 304 are provided for receiving coils 284 and 286. However, notches 302 and 304 are offset in opposite directions relative to the axis of winding form 292 while the bases 306 and 308 of notches 302 and 304 respectively are aligned in parallel relation and skewed from the bases 310 and 312 of notches 298 and 300 respectively. Coil 286 is adapted to produce a magnetic field along skewed axis 290 represented by vector 314. Coil 284 is adapted to selectively produce any one of the magnetic fields represented by vectors 316, 318, 320 and 322, which are also aligned along skewed axis 290. The driving circuit 324 of FIG. 19 includes switch means responsive to the 1, 2, and 8 positions of the binary coded input signal. The circuitry of the 2, 4 and 8 position switches of the embodiment of FIG. 19 is identical with the corresponding circuitry of the corresponding switches of the embodiment of FIG. l6,'with coil 182 of FIG. 16 being replaced by coil 284 of FIG. 19. Accordingly, like reference numerals have been ap plied to like elemenmts on FIG. 19 and reference is had to the description in connection with FIG. 16 for this portion of driving circuit 324. The energization of coils 274 and 286 are governed by binary 1 position switch means 326. Said switch means includes an armature 327 connected by line 328, resistor 329, and line 330 to terminal 280 of coil 272, the other terminal of said coil being connected along line 331 to ground. Armature 327 is adapted to engage fixed contact 332 when a 0 is detected at said binary 1 position, said fixed terminal being connected along line 333, resistor 334 and lines 335 and 215 to positive terminal 204 of the power source. Armature 327 is adapted to engage fixed terminal 336 of switch means 326 when a l is present at said 1 position of the binary code. Fixed terminal 336 is connected along line 337, coil 286, line 338, resistor 339 and lines 340 and 220 to negative terminal 206 of said power source.

The foregoing arrangement produces a decimal 0 position aligned with the magnetic field represented by vector 278, which in turn is aligned with axis 276. The

decimal 1 position is represented by the vector sum of the magnetic fields represented by vectors 282 and 314. The resultant magnetic field of decimal position 1 is represented by dashed'line 342. The decimal position 2 is produced by a sum of the magnetic fields represented by vectors 278 and 316 and is represented by dashed line 344. Decimal position 3 is produced by the magnetic field represented by the sum of vectors 282, 314 and 316 and is represented by dashed line 346.

Similarly, decimal positions 4, 6 and 8 are produced by the sum of the magnetic field represented by vector 278 and vectors 318, 322 and 320 respectively, said resultant magnetic fields being represented by dashed lines 348, 350 and 352 respectively. The decimal 5, 7 and 9 positions are produced by the vector sum of the magnetic field represented by vectors 282 and 314, and vectors 318, 322 and 320 respectively. The resultant magnetic fieldsof said positions are represented by dashed lines 354, 356 and 358 respectively.

The embodiment of FIGS. l7, l8 and 19 produces eleven substantially equally spaced position, but through the use of only three coils.

As used herein, the switch means schematically shown in FIGS. 13, 16 and 19 may take any desired form including relay operated armatures or electronic circuitry, as desired. The precise form of said switch means does not form a part of this invention.

In some applications of the arrangement according to the invention, it is desirable to provide means for retaining permanent magnet 75 in the last alignment thereof upon the deenergization of the coils. In the embodiment of FIG. 2, this result is produced by means of a locking star member 370 mounted on end plate 24 in symmetrical alignment with shaft 62. As more particularly shown in FIG. 4, locking star 370 consists of eleven radially extending arms 372 each positioned in one of the alignments of the resultant magnetic field produced by the winding of numerical display 10. In the embodiment of locking star 370shown in FIG. 4, said eleven arms are equally spaced, but, if desired, they could be spaced to align with the precise alignments of the the resultant magnetic field produced by the coil structure of the particular numerical display device according to the invention. Locking star member 370 performs the locking or memory function because of the tendancy of permanent magnet 75 to line up with the arms 372 thereof. An alternate approach to the provision of locking meansis shown in FIGS. and 6 wherein winding form 34 is provided with a modified magnetic core 374. One surface of said magnetic core, preferably the surface facing permanent magnet 75 is formed with eleven spaced V-shaped notches 376 projecting radially inwardly from peripheral edge 378. Notches 376 define a plurality of radially extending arms 380 in said surface of core 374. Said arms correspond to the arms of locking star 370 and function in a like manner. Locking star 370 is preferably formed of a low coercivity magnetic material. Other locking or memory arrangements may be incorporated in the numerical display devices according to the invention such as spaced pins of magnetic material projecting from magnetic core 40 or pins of said magnetic material mounted in spaced relation on casing 14.

Referring now to FIG. 7, an alternate construction of the permanent magnet of the numerical display device according to the invention is shown mounted on sahft 62 and symbol bearing member 72. Specifically, in

place of bar magnet which has the poles 76 and 77 thereof aligned radially relative to shaft 56, the embodiment of FIG. 7 is provided with a pair of bar magnets 382 and 384 having the poles thereof aligned axially relative to shaft 62. Thus, permanent magnets 382 would have a north pole defined at surface 386 thereof and a south pole defined at surface 388 thereof. In like manner, permanent magnet 384 would have a north pole at surface 390 and a south pole at surface 392 thereof. Permanent magnets 382 and 384 are mounted by their respective surfaces 388 and 390 to flux keeper 394. Said flux keeper is preferably a rectangular bar of soft magnetic material adapted to provide a flux path between the south pole of magnet 382 and the north pole of magnet 384. Lines of flux generated by the coils of the numerical display device according to the invention are shown schematically by dashed lines 396, the effect of the magnetic core of said numerical display device being ignored. As shown in FIG. 7, substantially all of the magnetic flux generated by the coils follows the magnetic path defined by permanent magnets 382 and 384 and flux keeper 394. The embodiment of FIG. 7 is relatively insensitive to external magnetic fields, the rotatable structure reacting to such external fields as if it were unmagnitized. Shielding would be completed by forming end plates 22 and 24 of low coercivity magnetic material. Permanent magnets 382 and 384 and flux keeper 394 are symmetrically balanced relative to shaft 62 to minimize drag.

A further embodiment of the numerical display device according to the invention is shown in FIGS. 8 and 9. The casing, end plates and printed circuit board portions of said embodiment are identical to the like elements of the embodiment of FIGS. 2 and 3 and like reference numerals have been assigned to these components. Mounted within casing 14 of numerical display device 400 is winding form 402, preferably formed from a plastic material. Said winding form is in the shape of a hollow cross. The winding form is mounted on printed circuit board 26 by means of four standoff elements 404. Coils 406, 408, 410 and 412 are wound about said winding form. Coils 406 and 408 are wound orthagonally relative to' coils 410 and 412 and operate in a manner similar to coils 48, 50, 52 and 54 of the embodiment of FIGS. 2 and 3.

The hollow center 414 of winding form 402 is dimensioned to receive a permanent bar magnet 416. Permanent bar magnet 416 is mounted on bearing 418 which in turn is mounted on freely rotatable shaft 420. Bearing 416 extends through a central aperture in winding form 402 and is supported thereon and at V-bearing 422. Said bar magnet is formed with a north pole at end 424 thereof and a south pole at end 426 thereof. Mounted on the end of sahft 420 spaced from V- bearing 422 is a symbol bearing member 428 similar in construction to symbol bearing member 72 of the embodiment of FIGS. 2 and 3. Mounted on printed circuit board 26 and dimensioned so as to encompass the coils and winding form is annular flux keeper 430.

The embodiment of FIGS. 8 and 9 functions in the same manner as the embodiment of FIGS. 2 and 3. However, the embodiment of FIGS. 8 and 9 is relatively easy to shield from the adverse effect of the interaction with the magnetic field of an adjacent numerical display device. Further, bearing friction is minimized due to the absence of magnetic forces pulling the magnet on to the bearing. These advantages are countered by the disadvantage of the more difficult assembly procedures required in connection with this embodiment. Annular flux keeper 430 is formed of a soft magnetic material and serves to guide the magnetic flux so that permanent magnet 416 aligns with the magnetic field produced by the coil. In the absence of said flux keeper, permanent magnet 416 would have two stable positions, neither of which are orthagonal to the coil producing the field due to the fringing field of the coil.

A further embodiment of the numerical display according to the invention is shown in FIGS. 10 and 11. In this embodiment the casing, end plates and printed circuit board are substantially identical to the like elements in the embodiment of FIGS. 2 and 3 and like reference numerals have been applied thereto. In place of the winding form and core of the embodiment of FIGS. 2 and 3, the casing 14 of numerical display 450 is provided with a core 452 shaped in the form of a cross. Said core is formed of laminated plates of soft magnetic material. The core is positioned relative to printed circuit board 26 by means of bushing 454 and is formed with a central aperture 456 therethrough. A bobbin 458 is mounted on each of the four arms of core 452 and coils 460, 462, 464 and 466 are wound on respective ones of said bobbin. These bobbin wound coils produce magnetic fields in the region thereof which may be summed and aligned in the same manner as the coils of the embodiment of FIGS. 2 and 3.

A shaft 468 extends through the central aperture 456 in core 452 and is supported at one end by the bearing 470 and along its length by bearings 454 and 472. Secured to the other end of shaft 468 is a centering disc 474. Such centering disc is retained on the shaft by the cooperation of flange 476 and cap 478 of shaft 468. An annular permanent magnet 480 is mounted to the periphery of centering disc 474. Said permanent magnet is formed with a discrete north pole in region 482 and a discrete south pole in region 484 and is adapted to seek alignment with the magnetic field generated by coils 460, 462, 464 and 466. Mounted on the periphery of annular permanent magnet 480 is an annular flux keeper 486 having spaced symbols mounted on the outer face 488 thereof. Thus, annular flux keeper serves both to confine the flux within the device as well as to carry the symbol for registration with viewing window 12.

The embodiment of FIGS. 10 and 11 operates in the same manner as the embodiment of FIGS. 2 and 3 and the core and winding structure of the embodiment of FIGS. 2 and 3 may be substituted for the core and winding structure of the embodiment of FIGS. 10 and 11. One advantage of the embodiment of FIGS. 10 and 11 is the small air gap between the permanent magnet and the core which compensates, to some measure, for the increased inertia of the arrangement. While in the embodiment of FIGS. 10 and 11, the annular permanent magnet has its poles spaced 180, said poles may be spaced less than l80, thereby avoiding the problem of 180 reversal.

Still another embodiment of the arrangement according to the invention is shown in FIGS. and 21. The end plate housing and printed circuit board of this embodiment are substantially identical to the embodiment of FIGS. 2 and 3 and like reference numerals have been applied thereto. Mounted within housing 14 of numerical display device 500 are a pair of spaced printed circuit boards 502 and 504 having on the facing surfaces thereof 506 and 508 respectively, printed circuit coils. As more particularly shown in FIG. 21, each circuit board has four printed circuit coils 510, 512, 514 and 516. Printed circuit boards 502 and 504 are each mounted on respective flux keeper boards 518 and 520. The entire assembly is mounted on printed circuit board 26 by means of standoff members 522. Printed circuit boards 502 and 504 are maintained in spaced relation by support members 524. Each of said printed circuit boards and flux keeper boards are formed with a central aperture 526 adapted to receive bushings 528. A shaft 530 rides in said bushing and in V-bearing 532 mounted on end plate 22. Mounted on the other end of shaft 530 is symbol bearing member 534 similar in construction and function to the symbol bearing member of the embodiment of FIGS. 2 and 3. Mounted centrally on shaft 528 is a permanent bar magnet 536 having a north pole at end 538 and a south pole at end 540. When printed coil 510 is connected in series with printed coil 512 by connecting terminal 542 of coil 510 to terminal 544 of coil 512, and the series connection of coils 510 and 512 are energized, a magnetic field is produced in the region of permanent magnet 536 analogous to the field produced by the coils of the embodiment of FIGS. 2 and 3. Similarly, terminal 546 of printed coil 514 would be connected to terminal 548 of printed coil 516. In this manner, each printed circuit board may correspond to a pair of orthagonally wound conventional coils. The operation of the embodiment of FIGS. 20 and 21 is substantially identical to the operation of the previously described embodiments of the invention. The flux keepers 518 and 520 are formed of soft magnetic material and serve to retain the flux path. The advantage of the embodiment of FIGS. 20 and 21 is that the air gaps may be made extremely small and the entire device may be made extremely thin and compact. Further, having the coils on opposed sides of the permanent magnet balances the forces on said magnet and minimizes the drag caused by torsional forces on the bar magnet and the drawing of shaft 530 against V- bearing 532. Since, in effect, flux keepers 518 and 520 also serve as a shield, end walls 22 and 24 need not serve the shielding function.

It will thus be seen that the objects set forth above, and those made apparent from the preceding description, are efficiently attained, and since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

What is claimed is:

l. A numerical display device comprising a fixed central winding form means; electrically energizable coil means mounted on said central winding form means for selectively providing a magnetic field selectively oriented in each of a plurality of discrete alignments in the region adjacent said coil means; permanent magnet means mounted for free rotation about an axis of rotation in said magnetic field for selectively assuming a plurality of discretely oriented alignments respectively associated with each of said magnetic field alignments,

said alignments being angularly spaced about said axis of rotation, at least the portion of the magnetic field oriented in each of said plurality of discrete alignments extending at least in part substantially parallel to said axis of rotation through the path of rotation of said permanent magnet means, said coil means and said permanent magnet means being in side-by-side relation in separate essentially parallelplanes along said axis of rotation; and symbol carrying means mounted for rotation with said permanent magnet means, said symbol carrying meansbeing formed with an outer face having symbols spaced thereon for selective positioning at a predetermined location in response to selective ones of said discrete alignments of said magnetic field.

2. A numerical display device as recited in claim 1, wherein said permanent magnet means includes bar magnet means having north and south poles spaced substantially equal distances from said axis of rotation.

3. A numerical display device as recited in claim 1, wherein said permanent magnet means includes flux keeper means formed of a magnetic material and a pair of permanent magnets mounted in spaced relation on said flux keeper means, one of said permanent magnets having its north pole facing said coil means and its south pole engaging said flux keeper means, the other of said permanent magnets having its south pole facing said coil means and its north pole engaging said flux keeper means, the assembly of said permanent magnets and flux keeper means being positioned on said axis of rotation with the respective north and south poles of said permanent magnets facing said coil means being spaced substantially equal distances from said axis of rotation.

4. A numerical display device as recited in claim 1, wherein said winding form-means is provided with a cylindrical well, said numerical display device including magnetic core means positioned in said winding form well and formed symmetrically relative to said axis of rotation, said coil means extending about said winding form means and core means. 7

5. A numerical display device as recited in claim 4, wherein said core means has a surface extending substantially normally to said axis of rotation, said surface being formed with a plurality of projections extending radially therealong relative to said axis of rotation, at least one of said projections being in registration with and corresponding to each of said discrete alignments of said magnetic field.

6. A numerical display device as recited in claim 1, including locking means formed of a magnetic material and having discrete portions thereof positioned at each of said plurality of discrete alignments of said magnetic field.

7. A numerical display device as recited in claim 6, wherein said locking means includes a locking star member having a center portion positioned on said axis of rotation and a plurality of arm members extending in a radial direction from said center portion and said axis of rotation, one of said arm portions being aligned with each of said plurality of discrete alignments of said magnetic field.

8. A numerical display device as recited in claim 7, wherein said coil means, said permanent magnet means and said locking star member are positioned in side-byside relation along said axis of rotation.

9. A numerical display device as recited in claim 1, wherein said winding form means includes a central support member including a center portion aligned substantially with said axis of rotation and a plurality of arms projecting in a radial direction from said center portion and said axis of rotation, and bobbin means mounted on at least a selected two of said arms angularly spaced about said axis of rotation less than said coil means being wound on said bobbins.

10. A numerical display device as recited in claim 9, wherein said supportmember is shaped substantially as a cross, and including bobbins mounted on each of said four arms for receiving said coil means.

11. A numerical display device as recited in claim 9, wherein said support member is formed of magnetic material for serving as a core for said winding means.

12. A numerical display device as recited in claim 1, wherein said coil means includes printed circuit coil means mounted on said winding form means, said permanent magnet means and said printed circuit coil means being aligned in side-by-side relation along said axis of rotation, at least a portion of said winding form means defining flux keeper means for providing a path for the flux produced by said printed circuit coil means.

13. A numerical display device as recited in claim 12, wherein said printed circuit coil means defines a plurality of coils, each of said coils being defined by first and second printed circuit coil portions an gularly spaced on said winding form means relative to said axis of rotation, said first and second printed circuit coil portions being connected in series for the production of a resultant magnetic field of selected annular alignment relative to said axis of rotation, each of the plurality of discrete alignments of said coil means magnetic field being defined by the sum of one or more of the resultant magnetic field of said coils.

14. A numerical display device as recited in claim 12, wherein said winding form means includes at least a pair of winding form boards spaced along said axis of rotation, said printed circuit coil means being mounted on the facing surfaces of said pair of winding form boards, said permanent magnet means being mounted for free rotation in the region intermediate said winding form boards.

15. A numerical'display device as recited in claim 1, wherein said coil means includes first and second coil members positioned to produce respective magnetic fields substantially aligned along a first axis passing through said axis of rotation and third and fourth coil members positioned to produce magnetic fields aligned along a second axis passing through said axis of rotation and substantially normal to said first axis.

16. A numerical display device as recited in claim 15, and including driving circuit means for providing energizing current to said coil means, said driving circuit means including switch means responsive to the presence of a 0 and l signal at each of four respective binary code positions and circuit means connecting said switch means and said coil members for the selective energization of said coil members by energizing currents of selected values, the magnetic field produced by said coil means at each of said discrete alignments corresponding to the sum of the magnetic fields produced by the energization of selected pairs of said coils by selected energizing currents in response to the state of said switch means, no two of said discrete alignments being spaced exactly 180 relative to said axis of rotation.

17. A numerical display device as recited in claim 16, wherein said circuit means includes resistive means for selectively controlling the value of the energizing cur rent applied to each of said coil members at each state of said switch means.

18. A numerical display device as recited in claim 16, wherein said driving circuit means includes resistive means connected in series with said four coil members for limiting the power dissipation in said coil members.

19. A numerical display device as recited in claim 18, wherein said series-connected resistive means has nonlinear resistive characteristics, the resistance thereof increasing with increased current passing therethrough, for a proportionally increased reduction in power dissipation as the current passing through said coil members increases due to the selected states of said switch means.

20. A numerical display device as recited in claim 16, wherein said driving circuit means includes non-linear resistive means connected in series with at least one selected pair of said coil members, the resistance of said non-linear resistive means increasing with increased current, for the selective angular positioning of certain of the discrete alignments of the coil means magnetic field.

21. A numerical display device as recited in claim 1, including driving circuit means for the selective energization of said coil means, said coil means including at least three coil members, said driving circuit means including switch means responsive to the O and l signals at each of at least four binary code positions, and circuit means for connecting said switch means and winding members for the selective application of energizing currents of selected magnitude to said coil members in response to the state of said switch means for the production of at least ten distinct alignments of said winding means magnetic field, no two of said alignments being spaced 180 relative to said axis of rotation, the winding means magnetic field at each of said discrete alignments being represented by the sum of the magnetic field produced by the then energized coil members.

22. A numerical display device as recited in claim 1, wherein said coil means includes a first coil member positioned to produce a magnetic field substantially 23. A numerical display device as recited in claim 22, including driving circuit means having switch means responsive to the O and 1 signals at each of at least four binary code positions, first circuit means for selectively connecting said first and second or said first and third coil members in series in response to the signal at the lowest of said binary code positions in response to the state of the switch means associated with said lowest binary code position, and second circuit means for selectively connecting said switch means associated with the balance of said decimal positions to said fourth coil member for the application of selected energizing currents to said fourth coil member in response to the state of said balance of said switch means.

24. A numerical display device as recited in claim 1, wherein said coil means includes a first coil member adapted to produce a field aligned with said first axis passing through said axis of rotation and second and third coil members adapted to produce a magnetic field aligned with a second axis passing through said axis of rotation and skewed from said first axis.

25. A numerical display device as recited in claim 24, including driving circuit means having at least four switch means responsive to the 0 and '1 signal at each of four binary code positions respectively, first circuit means for selectively applying an energizing current of a selected value to the series combination of said first and second coil members or to said first coil member depending on the state of the switch means associated with the lowest of said binary code positions, and second circuit means for applying a selected energizing current of one of a plurality of values to said third coil member in response to the state of the others of said switch means, said energizing currents being selected so that the no two of the discrete alignments of said winding means magnetic field are spaced exactly apart relative to said axis of rotation.

26. A numerical display device as recited in claim 25, wherein said first and second circuit means are adapted to apply energizing currents to said coil members for the production of eleven substantially equally spaced discrete alignments of said winding means magnetic field.

27. A numerical display device as recited in claim 1, wherein said symbol bearing means includes a cupshaped symbol bearing member having said symbols on the outer face of the annular portion thereof, said cupshaped member being formed of foam plastic. 

1. A numerical display device comprising a fixed central winding form means; electrically energizable coil means mounted on said central winding form means for selectively providing a magnetic field selectively oriented in each of a plurality of discrete alignments in the region adjacent said coil means; permanent magnet means mounted for free rotation about an axis of rotation in said magnetic field for selectively assuming a plurality of discretely oriented alignments respectively associated with each of said magnetic field alignments, said alignments being angularly spaced about said axis of rotation, at least the portion of the magnetic field oriented in each of said plurality of discrete alignments extending at least in part substantially parallel to said axis of rotation through the path of rotation of said permanent magnet means, said coil means and said permanent magnet means being in side-by-side relation in separate essentially parallel planes along said axis of rotation; and symbol carrying means mounted for rotation with said permanent magnet means, said symbol carrying means being formed with an outer face having symbols spaced thereon for selective positioning at a predetermined location in response to selective ones of said discrete alignments of said magnetic field.
 2. A numerical display device as recited in claim 1, wherein said permanent magnet means includes bar magnet means having north and south poles spaced substantially equal distances from said axis of rotation.
 3. A numerical display device as recited in claim 1, wherein said permanent magnet means includes flux keeper means formed of a magnetic material and a pair of permanent magnets mounted in spaced relation on said flux keeper means, one of said permanent magnets having its north pole facing said coil means and its south pole engaging said flux keeper means, the other of said permanent magnets having its south pole facing said coil means and its north pole engaging said flux keeper means, the assembly of said permanent magnets and flux keeper means being positioned on said axis of rotation with the respective north and south poles of said permanent magnets facing said coil means being spaced substantially equal distances from said axis of rotation.
 4. A numerical display device as recited in claim 1, wherein said winding form means is provided with a cylindrical well, said numerical display device including magnetic core means positioned in said winding form well and formed symmetrically relative to said axis of rotation, said coil means extending about said winding form means and core means.
 5. A numerical display device as recited in claim 4, wherein said core means has a surface extending substantially normally to said axis of rotation, said Surface being formed with a plurality of projections extending radially therealong relative to said axis of rotation, at least one of said projections being in registration with and corresponding to each of said discrete alignments of said magnetic field.
 6. A numerical display device as recited in claim 1, including locking means formed of a magnetic material and having discrete portions thereof positioned at each of said plurality of discrete alignments of said magnetic field.
 7. A numerical display device as recited in claim 6, wherein said locking means includes a locking star member having a center portion positioned on said axis of rotation and a plurality of arm members extending in a radial direction from said center portion and said axis of rotation, one of said arm portions being aligned with each of said plurality of discrete alignments of said magnetic field.
 8. A numerical display device as recited in claim 7, wherein said coil means, said permanent magnet means and said locking star member are positioned in side-by-side relation along said axis of rotation.
 9. A numerical display device as recited in claim 1, wherein said winding form means includes a central support member including a center portion aligned substantially with said axis of rotation and a plurality of arms projecting in a radial direction from said center portion and said axis of rotation, and bobbin means mounted on at least a selected two of said arms angularly spaced about said axis of rotation less than 180*, said coil means being wound on said bobbins.
 10. A numerical display device as recited in claim 9, wherein said support member is shaped substantially as a cross, and including bobbins mounted on each of said four arms for receiving said coil means.
 11. A numerical display device as recited in claim 9, wherein said support member is formed of magnetic material for serving as a core for said winding means.
 12. A numerical display device as recited in claim 1, wherein said coil means includes printed circuit coil means mounted on said winding form means, said permanent magnet means and said printed circuit coil means being aligned in side-by-side relation along said axis of rotation, at least a portion of said winding form means defining flux keeper means for providing a path for the flux produced by said printed circuit coil means.
 13. A numerical display device as recited in claim 12, wherein said printed circuit coil means defines a plurality of coils, each of said coils being defined by first and second printed circuit coil portions angularly spaced on said winding form means relative to said axis of rotation, said first and second printed circuit coil portions being connected in series for the production of a resultant magnetic field of selected annular alignment relative to said axis of rotation, each of the plurality of discrete alignments of said coil means magnetic field being defined by the sum of one or more of the resultant magnetic field of said coils.
 14. A numerical display device as recited in claim 12, wherein said winding form means includes at least a pair of winding form boards spaced along said axis of rotation, said printed circuit coil means being mounted on the facing surfaces of said pair of winding form boards, said permanent magnet means being mounted for free rotation in the region intermediate said winding form boards.
 15. A numerical display device as recited in claim 1, wherein said coil means includes first and second coil members positioned to produce respective magnetic fields substantially aligned along a first axis passing through said axis of rotation and third and fourth coil members positioned to produce magnetic fields aligned along a second axis passing through said axis of rotation and substantially normal to said first axis.
 16. A numerical display device as recited in claim 15, and including driving circuit means for providing energizing current to said coil means, said driving circuit means incluDing switch means responsive to the presence of a 0 and 1 signal at each of four respective binary code positions and circuit means connecting said switch means and said coil members for the selective energization of said coil members by energizing currents of selected values, the magnetic field produced by said coil means at each of said discrete alignments corresponding to the sum of the magnetic fields produced by the energization of selected pairs of said coils by selected energizing currents in response to the state of said switch means, no two of said discrete alignments being spaced exactly 180* relative to said axis of rotation.
 17. A numerical display device as recited in claim 16, wherein said circuit means includes resistive means for selectively controlling the value of the energizing current applied to each of said coil members at each state of said switch means.
 18. A numerical display device as recited in claim 16, wherein said driving circuit means includes resistive means connected in series with said four coil members for limiting the power dissipation in said coil members.
 19. A numerical display device as recited in claim 18, wherein said series-connected resistive means has non-linear resistive characteristics, the resistance thereof increasing with increased current passing therethrough, for a proportionally increased reduction in power dissipation as the current passing through said coil members increases due to the selected states of said switch means.
 20. A numerical display device as recited in claim 16, wherein said driving circuit means includes non-linear resistive means connected in series with at least one selected pair of said coil members, the resistance of said non-linear resistive means increasing with increased current, for the selective angular positioning of certain of the discrete alignments of the coil means magnetic field.
 21. A numerical display device as recited in claim 1, including driving circuit means for the selective energization of said coil means, said coil means including at least three coil members, said driving circuit means including switch means responsive to the 0 and 1 signals at each of at least four binary code positions, and circuit means for connecting said switch means and winding members for the selective application of energizing currents of selected magnitude to said coil members in response to the state of said switch means for the production of at least ten distinct alignments of said winding means magnetic field, no two of said alignments being spaced 180* relative to said axis of rotation, the winding means magnetic field at each of said discrete alignments being represented by the sum of the magnetic field produced by the then energized coil members.
 22. A numerical display device as recited in claim 1, wherein said coil means includes a first coil member positioned to produce a magnetic field substantially along a first axis passing through said axis of rotation and second, third and fourth coil members positioned to produce respective magnetic fields aligned substantially along a second axis passing through said axis of rotation and substantially normal to said first axis.
 23. A numerical display device as recited in claim 22, including driving circuit means having switch means responsive to the 0 and 1 signals at each of at least four binary code positions, first circuit means for selectively connecting said first and second or said first and third coil members in series in response to the signal at the lowest of said binary code positions in response to the state of the switch means associated with said lowest binary code position, and second circuit means for selectively connecting said switch means associated with the balance of said decimal positions to said fourth coil member for the application of selected energizing currents to said fourth coil member in response to the state of said balance of said switch means.
 24. A numerical display device as recited in claim 1, wherein said coil means includes a first coil member adapted to produce a field aligned with said first axis passing through said axis of rotation and second and third coil members adapted to produce a magnetic field aligned with a second axis passing through said axis of rotation and skewed from said first axis.
 25. A numerical display device as recited in claim 24, including driving circuit means having at least four switch means responsive to the 0 and 1 signal at each of four binary code positions respectively, first circuit means for selectively applying an energizing current of a selected value to the series combination of said first and second coil members or to said first coil member depending on the state of the switch means associated with the lowest of said binary code positions, and second circuit means for applying a selected energizing current of one of a plurality of values to said third coil member in response to the state of the others of said switch means, said energizing currents being selected so that the no two of the discrete alignments of said winding means magnetic field are spaced exactly 180* apart relative to said axis of rotation.
 26. A numerical display device as recited in claim 25, wherein said first and second circuit means are adapted to apply energizing currents to said coil members for the production of eleven substantially equally spaced discrete alignments of said winding means magnetic field.
 27. A numerical display device as recited in claim 1, wherein said symbol bearing means includes a cup-shaped symbol bearing member having said symbols on the outer face of the annular portion thereof, said cup-shaped member being formed of foam plastic. 